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Posted by cheeku on May 16, 2007, 11:43 am
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On May 16, 5:44 pm, B...@hotmail.co.uk wrote:
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> > On 14.05.2007 19:22 cheeku wrote
>
> > > hi.....
> > > can somebody explain what udld is ?
> > > i went through cisco's explanation.....but could'nt follow....
> > > thankyou
>
> > What is unclear?
>
> > UDLD is a Layer 2 protocol that works with Layer 1 mechanisms to
> > determine the physical status of a link. At Layer 1, autonegotiation
> > takes care of physical signaling and fault detection. UDLD performs
> > tasks that autonegotiation cannot perform, such as detecting the
> > identities of neighbors and shutting down misconnected ports. When you
> > enable both autonegotiation and UDLD, Layer 1 and 2 detections work
> > together to prevent physical and logical unidirectional connections and
> > the malfunctioning of other protocols.
>
> > Arnold
>
> Maybe it's the purpose that is not clear?
>
> In the case of a 10M or 100M UTP ethernet (10BaseT or 100BaseT),
> link when you connect two devices each will display
> a green light indicating that the link is "up".
>
> Lets call the two devices A and B.
>
> The problem occurs when for example the cable is faulty
> and the signal path from A to B is interrupted but
> the path from B to A is not. B will correctly
> show "link down" but A will show "Link up".
>
> This can cause dissruptive network failures
> since some upper layer protocols were not designed to
> operate correctly under these curcumstances.
> e.g. Spanning Tree, RIP.
>
> OSPF, BGP for example do detect this type of failure
> and are not affected.
>
> Gigabit Ethernet had the functionallity of UDLD built in
> (to layer 1) and so it is not necessary or applicable for GBE.- Hide quoted
text -
>
> - Show quoted text -
thank you....!!!!!!
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